The present invention relates to a fuel feed apparatus where fuel is supplied into a sub tank by a jet pump and sucked by a fuel pump to be discharged.
In general, an in-tank type fuel feed apparatus is disposed in a fuel tank for sucking fuel in the fuel tank and discharging the fuel. In such a fuel feed apparatus, fuel is apt to be charged with static electricity caused by friction between fuel discharged by a fuel pump in the fuel feed apparatus and a fuel outlet pipe, or between fuel discharged by a fuel pump and a filter element in a fuel filter. When fuel discharged by the fuel pump is charged with static electricity, members defining a passage downstream of the fuel pump and peripheral members around the passage downstream of the fuel pump are charged.
When a charged nonconductive member discharges its static electricity as corona discharge, discharge energy itself is low. However, if the charged nonconductive member exists near a non-grounded conductive member, an induction charge arises inside the non-grounded conductive member. Subsequently, if the non-grounded conductive member, in which induction charge is located near another conductive member, a spark may be caused between the conductive members, regardless whether the latter conductive member is grounded or not. Such a spark between the conductive members is apt to be caused in a condition such as low temperature, low vapor pressure of fuel and high air/fuel ratio (A/F) enough to be ignited in the fuel tank, for example. On the other hand, if a charge amount increases in the nonconductive member, the nonconductive members may cause dielectric breakdown. Accordingly, it is likely that a crack may be caused from the section where the dielectric breakdown is caused.
Generally, in an in-tank type fuel feed apparatus, a fuel feed pump is disposed in a sub tank. Here, the sub tank is accommodated in a fuel tank. A liquid level in the sub tank is controlled so that the fuel pump can suck fuel even if the liquid level in the fuel tank is decreased. In such a fuel feed apparatus, surplus fuel is returned from an engine and from a fuel pump. Such surplus fuel is supplied to a jet pump. Fuel in the fuel tank is sucked by negative pressure generated when the surplus fuel is jetted from a jet nozzle of the jet pump and is supplied to the sub tank.
In a fuel feed apparatus according to JP-A-11-324840, a fuel discharge pipe in a downstream of a fuel pump is electrically connected and grounded to prevent nonconductive members on the downstream side of the fuel pump from charging.